Subterranean deposits of natural resources such as gas, water, and crude oil are commonly recovered by drilling wellbores to tap subterranean formations or zones containing such deposits. Various fluids are employed in drilling a wellbore and preparing the wellbore and an adjacent subterranean formation for the recovery of material therefrom. For example, a drilling fluid or mud is usually circulated through a wellbore as it is being drilled to cool the bit, keep deposits confined to their respective formations during the drilling process, and bring drill cuttings to the surface.
Increased drilling activity has continued at greater depths in challenging geographic areas such as marine environments. Drilling fluids used during these recovery operations are often exposed to a range of temperatures as the drilling fluid moves from a platform structure to the beginning/bottom of the ocean floor. For example, a drilling fluid moving through a drill string or pipe from a platform structure to 30,000-40,000 feet of combined water depth and core substrata may experience temperatures ranging from 35° F. to 400° F. Drilling fluids are designed to display a set of rheological characteristics that are suitable for a particular recovery operation. One challenge to the use of drilling fluids in challenging geographic areas is the maintenance of desirable rheological characteristics over the range of environmental conditions to which the fluids are exposed. Thus an ongoing need exists for improved drilling fluids for use in challenging geographic areas.